Tensegrity is a structural principle based on the use of isolated components, such as rigid bars or struts (in compression), linked together by a continuous net of cables or tendons (in tension), in such a way that the rigid bars or struts do not touch each other.
The distribution of compression and tension forces within the structure is such that a tensegrity structure takes and maintains its shape without any direct contact or joint between the different rigid bars or struts.
Tensegrity structures may be deployable or not according to the technical field to which they pertain.
In the space industry, a deployable reflector with a tensegrity support has already been proposed in U.S. Pat. No. 6,542,132.
An advantage to use a tensegrity structure for such a deployable reflector is to diminish the risk of failure of the deployment. Indeed, in non-tensegrity structures, the joints between two rigid bars or struts raise the failure risks.
However, the quoted document proposes a prismatic structure wherein rigid bars extend from the periphery towards the centre.
Consequently, the rigid bars are quite long and, in practice, can hardly be stowed within the envelope of typical space launchers, even in the case of small scale structures.
Moreover, since the proposed prismatic structure is not symmetric with respect to any plane, perpendicular to the longitudinal axis of the structure, the stability of the structure in orbit is not optimal.
To the applicant's knowledge, this structure has not been used to date.
Former deployable structures do not present the drawbacks of the tensegrity structure proposed in U.S. Pat. No. 6,542,132.
In facts, these former deployable structures can be stowed within the envelope of typical space launchers and are also stable in orbit.
Such a deployable structure is proposed in U.S. Pat. No. 5,680,145. It is well-known to the experts in the field under the name “Astromesh”.
The “Astromesh” is composed of a ring-shaped support structure around a longitudinal axis which includes a series of upper rigid contour elements and lower contour elements which, when connected end-to-end, form an upper contour and a lower contour, kept separated by a number of vertical rigid struts.
This support structure allows obtaining a deployable structure which is substantially symmetric with respect to a transversal plane, perpendicular to the longitudinal axis (axis of symmetry) of the support structure itself. A good stability in orbit may thus be obtained.
However, the “Astromesh” structure is not a tensegrity structure, as the contour elements in the upper and lower rigid contour sequences are mounted with each other through joints without which the structure could not be stowed in the space launcher. Moreover, the vertical rigid struts are also mounted through rigid connecting members to said contour elements.
Consequently, the risk of failure of deployment is non-negligible.
Moreover, the number of rigid parts (contour elements and struts) increases the weight of the support structure, whereas it is preferable to have a low mass structure for a space launcher.